MADISON, Wis. A fundamental chemical pathway that all plants use to create an essential amino acid needed by all animals to make proteins has now been traced to two groups of ancient bacteria. The pathway is also known for making hundreds of chemicals, including a compound that makes wood strong and the pigments that make red wine red.
"We have been trying to unravel the source of the phenylalanine amino acid for some time," says Hiroshi Maeda, an assistant professor of botany at the University of Wisconsin-Madison. "Plants use this pathway to make natural products that are vital to plants and also to our food, medicine, fiber and fuel. One of the most important is lignin, found in the plant cell wall, which allows trees to stand tall and transport water."
Other scientists have traced plant metabolic pathways to fungi, "which are pretty close to plants in terms of evolution," Maeda says. "But in this case, the source is bacteria, which are more distant relatives."
In a study recently published in the online journal The Plant Cell, Maeda and his colleagues described how they traced the phenylalanine pathway to two groups of bacteria. "Our question was how plants can produce so many different kinds and amounts of these aromatics, particularly the phenylalanine-derived compounds," Maeda says.
During the study, Maeda and his colleagues, including John Jelesko of the Virginia Polytechnic Institute, compared the genetic sequence for the plant phenylalanine pathway enzymes to a genetic database covering numerous organisms. "We asked the computer to fish out similar sequences, and we got thousands of sequences," Maeda says. "We took the closer sequences and did phylogenetic analysis. Essentially we were asking, 'Who is your closest sibling?'"
They found that the plant sequence was most similar to a class of bacteria called Chlorobi and Bacteroidetes. "This was surprising because when people do a similar analysis for
|Contact: Hiroshi Maeda|
University of Wisconsin-Madison